In the specification, relevant terms used are abbreviated for gas chromatography as GC, liquid chromatography as LC, mass spectrometer as MS, apparatus combining gas chromatography and mass spectrometer as GC/MS, atmospheric pressure chemical ionization as APCI, chemical ionization as CI, electron impact as EI, and electro-spray ionization as ESI, respectively.
GC/MS is a well known analysis technology. APCI/MS is an apparatus for ionizing and detecting micro-amount of ingredients in a mixed sample at high sensitivity by using ion-molecular reaction, which is utilized for the analysis of micro-ingredients in environmental samples and bio-samples. JP-A No. 9-15207 discloses an analyzer at high sensitivity combining GC and APCI/MS for conducting analysis of various kinds of micro-impurities containing special gases for use in semiconductor production. In the apparatus, a sample gas separated by the column of GC is introduced in admixture with a carrier gas by way of a line to an APCI source and analyzed. JP-A No. 11-307041 discloses an apparatus in which a first ionization chamber for CI, a second ionization chamber for EI, and a mass analysis part are serially in adjacent with each other, and a passage port for passing ions is disposed between each of the ion sources. The sample gas enters the first ionization chamber and is introduced through the passage port into the second ionization chamber. During CI operation, the sample gas is ionized in a state of stopping the EI operation. During EI operation, the sample gas is ionized in a state of stopping the CI operation, and the introduced samples are analyzed by switching the two ion sources. JP-A No. 2000-357488 discloses an apparatus of separating ingredients flown out of LC by a branching tee and delivering the same to two ion sources of ESI and APCI. By switching the ion sources, they can be analyzed by two ionization methods. Further, JP-A No. 2001-93461 discloses a constitution of improving the sensitivity by making the gas flow different from the ion moving direction in APCI ionization by corona discharge using a needle electrode.